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Diffstat (limited to 'Documentation/ia64')
| -rw-r--r-- | Documentation/ia64/aliasing.rst | 246 | ||||
| -rw-r--r-- | Documentation/ia64/efirtc.rst | 144 | ||||
| -rw-r--r-- | Documentation/ia64/err_inject.rst | 1067 | ||||
| -rw-r--r-- | Documentation/ia64/features.rst | 3 | ||||
| -rw-r--r-- | Documentation/ia64/fsys.rst | 303 | ||||
| -rw-r--r-- | Documentation/ia64/ia64.rst | 49 | ||||
| -rw-r--r-- | Documentation/ia64/index.rst | 19 | ||||
| -rw-r--r-- | Documentation/ia64/irq-redir.rst | 80 | ||||
| -rw-r--r-- | Documentation/ia64/mca.rst | 198 | ||||
| -rw-r--r-- | Documentation/ia64/serial.rst | 165 |
10 files changed, 2274 insertions, 0 deletions
diff --git a/Documentation/ia64/aliasing.rst b/Documentation/ia64/aliasing.rst new file mode 100644 index 000000000..a08b36aba --- /dev/null +++ b/Documentation/ia64/aliasing.rst @@ -0,0 +1,246 @@ +================================== +Memory Attribute Aliasing on IA-64 +================================== + +Bjorn Helgaas <bjorn.helgaas@hp.com> + +May 4, 2006 + + +Memory Attributes +================= + + Itanium supports several attributes for virtual memory references. + The attribute is part of the virtual translation, i.e., it is + contained in the TLB entry. The ones of most interest to the Linux + kernel are: + + == ====================== + WB Write-back (cacheable) + UC Uncacheable + WC Write-coalescing + == ====================== + + System memory typically uses the WB attribute. The UC attribute is + used for memory-mapped I/O devices. The WC attribute is uncacheable + like UC is, but writes may be delayed and combined to increase + performance for things like frame buffers. + + The Itanium architecture requires that we avoid accessing the same + page with both a cacheable mapping and an uncacheable mapping[1]. + + The design of the chipset determines which attributes are supported + on which regions of the address space. For example, some chipsets + support either WB or UC access to main memory, while others support + only WB access. + +Memory Map +========== + + Platform firmware describes the physical memory map and the + supported attributes for each region. At boot-time, the kernel uses + the EFI GetMemoryMap() interface. ACPI can also describe memory + devices and the attributes they support, but Linux/ia64 currently + doesn't use this information. + + The kernel uses the efi_memmap table returned from GetMemoryMap() to + learn the attributes supported by each region of physical address + space. Unfortunately, this table does not completely describe the + address space because some machines omit some or all of the MMIO + regions from the map. + + The kernel maintains another table, kern_memmap, which describes the + memory Linux is actually using and the attribute for each region. + This contains only system memory; it does not contain MMIO space. + + The kern_memmap table typically contains only a subset of the system + memory described by the efi_memmap. Linux/ia64 can't use all memory + in the system because of constraints imposed by the identity mapping + scheme. + + The efi_memmap table is preserved unmodified because the original + boot-time information is required for kexec. + +Kernel Identify Mappings +======================== + + Linux/ia64 identity mappings are done with large pages, currently + either 16MB or 64MB, referred to as "granules." Cacheable mappings + are speculative[2], so the processor can read any location in the + page at any time, independent of the programmer's intentions. This + means that to avoid attribute aliasing, Linux can create a cacheable + identity mapping only when the entire granule supports cacheable + access. + + Therefore, kern_memmap contains only full granule-sized regions that + can referenced safely by an identity mapping. + + Uncacheable mappings are not speculative, so the processor will + generate UC accesses only to locations explicitly referenced by + software. This allows UC identity mappings to cover granules that + are only partially populated, or populated with a combination of UC + and WB regions. + +User Mappings +============= + + User mappings are typically done with 16K or 64K pages. The smaller + page size allows more flexibility because only 16K or 64K has to be + homogeneous with respect to memory attributes. + +Potential Attribute Aliasing Cases +================================== + + There are several ways the kernel creates new mappings: + +mmap of /dev/mem +---------------- + + This uses remap_pfn_range(), which creates user mappings. These + mappings may be either WB or UC. If the region being mapped + happens to be in kern_memmap, meaning that it may also be mapped + by a kernel identity mapping, the user mapping must use the same + attribute as the kernel mapping. + + If the region is not in kern_memmap, the user mapping should use + an attribute reported as being supported in the EFI memory map. + + Since the EFI memory map does not describe MMIO on some + machines, this should use an uncacheable mapping as a fallback. + +mmap of /sys/class/pci_bus/.../legacy_mem +----------------------------------------- + + This is very similar to mmap of /dev/mem, except that legacy_mem + only allows mmap of the one megabyte "legacy MMIO" area for a + specific PCI bus. Typically this is the first megabyte of + physical address space, but it may be different on machines with + several VGA devices. + + "X" uses this to access VGA frame buffers. Using legacy_mem + rather than /dev/mem allows multiple instances of X to talk to + different VGA cards. + + The /dev/mem mmap constraints apply. + +mmap of /proc/bus/pci/.../??.? +------------------------------ + + This is an MMIO mmap of PCI functions, which additionally may or + may not be requested as using the WC attribute. + + If WC is requested, and the region in kern_memmap is either WC + or UC, and the EFI memory map designates the region as WC, then + the WC mapping is allowed. + + Otherwise, the user mapping must use the same attribute as the + kernel mapping. + +read/write of /dev/mem +---------------------- + + This uses copy_from_user(), which implicitly uses a kernel + identity mapping. This is obviously safe for things in + kern_memmap. + + There may be corner cases of things that are not in kern_memmap, + but could be accessed this way. For example, registers in MMIO + space are not in kern_memmap, but could be accessed with a UC + mapping. This would not cause attribute aliasing. But + registers typically can be accessed only with four-byte or + eight-byte accesses, and the copy_from_user() path doesn't allow + any control over the access size, so this would be dangerous. + +ioremap() +--------- + + This returns a mapping for use inside the kernel. + + If the region is in kern_memmap, we should use the attribute + specified there. + + If the EFI memory map reports that the entire granule supports + WB, we should use that (granules that are partially reserved + or occupied by firmware do not appear in kern_memmap). + + If the granule contains non-WB memory, but we can cover the + region safely with kernel page table mappings, we can use + ioremap_page_range() as most other architectures do. + + Failing all of the above, we have to fall back to a UC mapping. + +Past Problem Cases +================== + +mmap of various MMIO regions from /dev/mem by "X" on Intel platforms +-------------------------------------------------------------------- + + The EFI memory map may not report these MMIO regions. + + These must be allowed so that X will work. This means that + when the EFI memory map is incomplete, every /dev/mem mmap must + succeed. It may create either WB or UC user mappings, depending + on whether the region is in kern_memmap or the EFI memory map. + +mmap of 0x0-0x9FFFF /dev/mem by "hwinfo" on HP sx1000 with VGA enabled +---------------------------------------------------------------------- + + The EFI memory map reports the following attributes: + + =============== ======= ================== + 0x00000-0x9FFFF WB only + 0xA0000-0xBFFFF UC only (VGA frame buffer) + 0xC0000-0xFFFFF WB only + =============== ======= ================== + + This mmap is done with user pages, not kernel identity mappings, + so it is safe to use WB mappings. + + The kernel VGA driver may ioremap the VGA frame buffer at 0xA0000, + which uses a granule-sized UC mapping. This granule will cover some + WB-only memory, but since UC is non-speculative, the processor will + never generate an uncacheable reference to the WB-only areas unless + the driver explicitly touches them. + +mmap of 0x0-0xFFFFF legacy_mem by "X" +------------------------------------- + + If the EFI memory map reports that the entire range supports the + same attributes, we can allow the mmap (and we will prefer WB if + supported, as is the case with HP sx[12]000 machines with VGA + disabled). + + If EFI reports the range as partly WB and partly UC (as on sx[12]000 + machines with VGA enabled), we must fail the mmap because there's no + safe attribute to use. + + If EFI reports some of the range but not all (as on Intel firmware + that doesn't report the VGA frame buffer at all), we should fail the + mmap and force the user to map just the specific region of interest. + +mmap of 0xA0000-0xBFFFF legacy_mem by "X" on HP sx1000 with VGA disabled +------------------------------------------------------------------------ + + The EFI memory map reports the following attributes:: + + 0x00000-0xFFFFF WB only (no VGA MMIO hole) + + This is a special case of the previous case, and the mmap should + fail for the same reason as above. + +read of /sys/devices/.../rom +---------------------------- + + For VGA devices, this may cause an ioremap() of 0xC0000. This + used to be done with a UC mapping, because the VGA frame buffer + at 0xA0000 prevents use of a WB granule. The UC mapping causes + an MCA on HP sx[12]000 chipsets. + + We should use WB page table mappings to avoid covering the VGA + frame buffer. + +Notes +===== + + [1] SDM rev 2.2, vol 2, sec 4.4.1. + [2] SDM rev 2.2, vol 2, sec 4.4.6. diff --git a/Documentation/ia64/efirtc.rst b/Documentation/ia64/efirtc.rst new file mode 100644 index 000000000..fd8328408 --- /dev/null +++ b/Documentation/ia64/efirtc.rst @@ -0,0 +1,144 @@ +========================== +EFI Real Time Clock driver +========================== + +S. Eranian <eranian@hpl.hp.com> + +March 2000 + +1. Introduction +=============== + +This document describes the efirtc.c driver has provided for +the IA-64 platform. + +The purpose of this driver is to supply an API for kernel and user applications +to get access to the Time Service offered by EFI version 0.92. + +EFI provides 4 calls one can make once the OS is booted: GetTime(), +SetTime(), GetWakeupTime(), SetWakeupTime() which are all supported by this +driver. We describe those calls as well the design of the driver in the +following sections. + +2. Design Decisions +=================== + +The original ideas was to provide a very simple driver to get access to, +at first, the time of day service. This is required in order to access, in a +portable way, the CMOS clock. A program like /sbin/hwclock uses such a clock +to initialize the system view of the time during boot. + +Because we wanted to minimize the impact on existing user-level apps using +the CMOS clock, we decided to expose an API that was very similar to the one +used today with the legacy RTC driver (driver/char/rtc.c). However, because +EFI provides a simpler services, not all ioctl() are available. Also +new ioctl()s have been introduced for things that EFI provides but not the +legacy. + +EFI uses a slightly different way of representing the time, noticeably +the reference date is different. Year is the using the full 4-digit format. +The Epoch is January 1st 1998. For backward compatibility reasons we don't +expose this new way of representing time. Instead we use something very +similar to the struct tm, i.e. struct rtc_time, as used by hwclock. +One of the reasons for doing it this way is to allow for EFI to still evolve +without necessarily impacting any of the user applications. The decoupling +enables flexibility and permits writing wrapper code is ncase things change. + +The driver exposes two interfaces, one via the device file and a set of +ioctl()s. The other is read-only via the /proc filesystem. + +As of today we don't offer a /proc/sys interface. + +To allow for a uniform interface between the legacy RTC and EFI time service, +we have created the include/linux/rtc.h header file to contain only the +"public" API of the two drivers. The specifics of the legacy RTC are still +in include/linux/mc146818rtc.h. + + +3. Time of day service +====================== + +The part of the driver gives access to the time of day service of EFI. +Two ioctl()s, compatible with the legacy RTC calls: + + Read the CMOS clock:: + + ioctl(d, RTC_RD_TIME, &rtc); + + Write the CMOS clock:: + + ioctl(d, RTC_SET_TIME, &rtc); + +The rtc is a pointer to a data structure defined in rtc.h which is close +to a struct tm:: + + struct rtc_time { + int tm_sec; + int tm_min; + int tm_hour; + int tm_mday; + int tm_mon; + int tm_year; + int tm_wday; + int tm_yday; + int tm_isdst; + }; + +The driver takes care of converting back an forth between the EFI time and +this format. + +Those two ioctl()s can be exercised with the hwclock command: + +For reading:: + + # /sbin/hwclock --show + Mon Mar 6 15:32:32 2000 -0.910248 seconds + +For setting:: + + # /sbin/hwclock --systohc + +Root privileges are required to be able to set the time of day. + +4. Wakeup Alarm service +======================= + +EFI provides an API by which one can program when a machine should wakeup, +i.e. reboot. This is very different from the alarm provided by the legacy +RTC which is some kind of interval timer alarm. For this reason we don't use +the same ioctl()s to get access to the service. Instead we have +introduced 2 news ioctl()s to the interface of an RTC. + +We have added 2 new ioctl()s that are specific to the EFI driver: + + Read the current state of the alarm:: + + ioctl(d, RTC_WKALM_RD, &wkt) + + Set the alarm or change its status:: + + ioctl(d, RTC_WKALM_SET, &wkt) + +The wkt structure encapsulates a struct rtc_time + 2 extra fields to get +status information:: + + struct rtc_wkalrm { + + unsigned char enabled; /* =1 if alarm is enabled */ + unsigned char pending; /* =1 if alarm is pending */ + + struct rtc_time time; + } + +As of today, none of the existing user-level apps supports this feature. +However writing such a program should be hard by simply using those two +ioctl(). + +Root privileges are required to be able to set the alarm. + +5. References +============= + +Checkout the following Web site for more information on EFI: + +http://developer.intel.com/technology/efi/ diff --git a/Documentation/ia64/err_inject.rst b/Documentation/ia64/err_inject.rst new file mode 100644 index 000000000..900f71e93 --- /dev/null +++ b/Documentation/ia64/err_inject.rst @@ -0,0 +1,1067 @@ +======================================== +IPF Machine Check (MC) error inject tool +======================================== + +IPF Machine Check (MC) error inject tool is used to inject MC +errors from Linux. The tool is a test bed for IPF MC work flow including +hardware correctable error handling, OS recoverable error handling, MC +event logging, etc. + +The tool includes two parts: a kernel driver and a user application +sample. The driver provides interface to PAL to inject error +and query error injection capabilities. The driver code is in +arch/ia64/kernel/err_inject.c. The application sample (shown below) +provides a combination of various errors and calls the driver's interface +(sysfs interface) to inject errors or query error injection capabilities. + +The tool can be used to test Intel IPF machine MC handling capabilities. +It's especially useful for people who can not access hardware MC injection +tool to inject error. It's also very useful to integrate with other +software test suits to do stressful testing on IPF. + +Below is a sample application as part of the whole tool. The sample +can be used as a working test tool. Or it can be expanded to include +more features. It also can be a integrated into a library or other user +application to have more thorough test. + +The sample application takes err.conf as error configuration input. GCC +compiles the code. After you install err_inject driver, you can run +this sample application to inject errors. + +Errata: Itanium 2 Processors Specification Update lists some errata against +the pal_mc_error_inject PAL procedure. The following err.conf has been tested +on latest Montecito PAL. + +err.conf:: + + #This is configuration file for err_inject_tool. + #The format of the each line is: + #cpu, loop, interval, err_type_info, err_struct_info, err_data_buffer + #where + # cpu: logical cpu number the error will be inject in. + # loop: times the error will be injected. + # interval: In second. every so often one error is injected. + # err_type_info, err_struct_info: PAL parameters. + # + #Note: All values are hex w/o or w/ 0x prefix. + + + #On cpu2, inject only total 0x10 errors, interval 5 seconds + #corrected, data cache, hier-2, physical addr(assigned by tool code). + #working on Montecito latest PAL. + 2, 10, 5, 4101, 95 + + #On cpu4, inject and consume total 0x10 errors, interval 5 seconds + #corrected, data cache, hier-2, physical addr(assigned by tool code). + #working on Montecito latest PAL. + 4, 10, 5, 4109, 95 + + #On cpu15, inject and consume total 0x10 errors, interval 5 seconds + #recoverable, DTR0, hier-2. + #working on Montecito latest PAL. + 0xf, 0x10, 5, 4249, 15 + +The sample application source code: + +err_injection_tool.c:: + + /* + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or + * NON INFRINGEMENT. See the GNU General Public License for more + * details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + * + * Copyright (C) 2006 Intel Co + * Fenghua Yu <fenghua.yu@intel.com> + * + */ + #include <sys/types.h> + #include <sys/stat.h> + #include <fcntl.h> + #include <stdio.h> + #include <sched.h> + #include <unistd.h> + #include <stdlib.h> + #include <stdarg.h> + #include <string.h> + #include <errno.h> + #include <time.h> + #include <sys/ipc.h> + #include <sys/sem.h> + #include <sys/wait.h> + #include <sys/mman.h> + #include <sys/shm.h> + + #define MAX_FN_SIZE 256 + #define MAX_BUF_SIZE 256 + #define DATA_BUF_SIZE 256 + #define NR_CPUS 512 + #define MAX_TASK_NUM 2048 + #define MIN_INTERVAL 5 // seconds + #define ERR_DATA_BUFFER_SIZE 3 // Three 8-byte. + #define PARA_FIELD_NUM 5 + #define MASK_SIZE (NR_CPUS/64) + #define PATH_FORMAT "/sys/devices/system/cpu/cpu%d/err_inject/" + + int sched_setaffinity(pid_t pid, unsigned int len, unsigned long *mask); + + int verbose; + #define vbprintf if (verbose) printf + + int log_info(int cpu, const char *fmt, ...) + { + FILE *log; + char fn[MAX_FN_SIZE]; + char buf[MAX_BUF_SIZE]; + va_list args; + + sprintf(fn, "%d.log", cpu); + log=fopen(fn, "a+"); + if (log==NULL) { + perror("Error open:"); + return -1; + } + + va_start(args, fmt); + vprintf(fmt, args); + memset(buf, 0, MAX_BUF_SIZE); + vsprintf(buf, fmt, args); + va_end(args); + + fwrite(buf, sizeof(buf), 1, log); + fclose(log); + + return 0; + } + + typedef unsigned long u64; + typedef unsigned int u32; + + typedef union err_type_info_u { + struct { + u64 mode : 3, /* 0-2 */ + err_inj : 3, /* 3-5 */ + err_sev : 2, /* 6-7 */ + err_struct : 5, /* 8-12 */ + struct_hier : 3, /* 13-15 */ + reserved : 48; /* 16-63 */ + } err_type_info_u; + u64 err_type_info; + } err_type_info_t; + + typedef union err_struct_info_u { + struct { + u64 siv : 1, /* 0 */ + c_t : 2, /* 1-2 */ + cl_p : 3, /* 3-5 */ + cl_id : 3, /* 6-8 */ + cl_dp : 1, /* 9 */ + reserved1 : 22, /* 10-31 */ + tiv : 1, /* 32 */ + trigger : 4, /* 33-36 */ + trigger_pl : 3, /* 37-39 */ + reserved2 : 24; /* 40-63 */ + } err_struct_info_cache; + struct { + u64 siv : 1, /* 0 */ + tt : 2, /* 1-2 */ + tc_tr : 2, /* 3-4 */ + tr_slot : 8, /* 5-12 */ + reserved1 : 19, /* 13-31 */ + tiv : 1, /* 32 */ + trigger : 4, /* 33-36 */ + trigger_pl : 3, /* 37-39 */ + reserved2 : 24; /* 40-63 */ + } err_struct_info_tlb; + struct { + u64 siv : 1, /* 0 */ + regfile_id : 4, /* 1-4 */ + reg_num : 7, /* 5-11 */ + reserved1 : 20, /* 12-31 */ + tiv : 1, /* 32 */ + trigger : 4, /* 33-36 */ + trigger_pl : 3, /* 37-39 */ + reserved2 : 24; /* 40-63 */ + } err_struct_info_register; + struct { + u64 reserved; + } err_struct_info_bus_processor_interconnect; + u64 err_struct_info; + } err_struct_info_t; + + typedef union err_data_buffer_u { + struct { + u64 trigger_addr; /* 0-63 */ + u64 inj_addr; /* 64-127 */ + u64 way : 5, /* 128-132 */ + index : 20, /* 133-152 */ + : 39; /* 153-191 */ + } err_data_buffer_cache; + struct { + u64 trigger_addr; /* 0-63 */ + u64 inj_addr; /* 64-127 */ + u64 way : 5, /* 128-132 */ + index : 20, /* 133-152 */ + reserved : 39; /* 153-191 */ + } err_data_buffer_tlb; + struct { + u64 trigger_addr; /* 0-63 */ + } err_data_buffer_register; + struct { + u64 reserved; /* 0-63 */ + } err_data_buffer_bus_processor_interconnect; + u64 err_data_buffer[ERR_DATA_BUFFER_SIZE]; + } err_data_buffer_t; + + typedef union capabilities_u { + struct { + u64 i : 1, + d : 1, + rv : 1, + tag : 1, + data : 1, + mesi : 1, + dp : 1, + reserved1 : 3, + pa : 1, + va : 1, + wi : 1, + reserved2 : 20, + trigger : 1, + trigger_pl : 1, + reserved3 : 30; + } capabilities_cache; + struct { + u64 d : 1, + i : 1, + rv : 1, + tc : 1, + tr : 1, + reserved1 : 27, + trigger : 1, + trigger_pl : 1, + reserved2 : 30; + } capabilities_tlb; + struct { + u64 gr_b0 : 1, + gr_b1 : 1, + fr : 1, + br : 1, + pr : 1, + ar : 1, + cr : 1, + rr : 1, + pkr : 1, + dbr : 1, + ibr : 1, + pmc : 1, + pmd : 1, + reserved1 : 3, + regnum : 1, + reserved2 : 15, + trigger : 1, + trigger_pl : 1, + reserved3 : 30; + } capabilities_register; + struct { + u64 reserved; + } capabilities_bus_processor_interconnect; + } capabilities_t; + + typedef struct resources_s { + u64 ibr0 : 1, + ibr2 : 1, + ibr4 : 1, + ibr6 : 1, + dbr0 : 1, + dbr2 : 1, + dbr4 : 1, + dbr6 : 1, + reserved : 48; + } resources_t; + + + long get_page_size(void) + { + long page_size=sysconf(_SC_PAGESIZE); + return page_size; + } + + #define PAGE_SIZE (get_page_size()==-1?0x4000:get_page_size()) + #define SHM_SIZE (2*PAGE_SIZE*NR_CPUS) + #define SHM_VA 0x2000000100000000 + + int shmid; + void *shmaddr; + + int create_shm(void) + { + key_t key; + char fn[MAX_FN_SIZE]; + + /* cpu0 is always existing */ + sprintf(fn, PATH_FORMAT, 0); + if ((key = ftok(fn, 's')) == -1) { + perror("ftok"); + return -1; + } + + shmid = shmget(key, SHM_SIZE, 0644 | IPC_CREAT); + if (shmid == -1) { + if (errno==EEXIST) { + shmid = shmget(key, SHM_SIZE, 0); + if (shmid == -1) { + perror("shmget"); + return -1; + } + } + else { + perror("shmget"); + return -1; + } + } + vbprintf("shmid=%d", shmid); + + /* connect to the segment: */ + shmaddr = shmat(shmid, (void *)SHM_VA, 0); + if (shmaddr == (void*)-1) { + perror("shmat"); + return -1; + } + + memset(shmaddr, 0, SHM_SIZE); + mlock(shmaddr, SHM_SIZE); + + return 0; + } + + int free_shm() + { + munlock(shmaddr, SHM_SIZE); + shmdt(shmaddr); + semctl(shmid, 0, IPC_RMID); + + return 0; + } + + #ifdef _SEM_SEMUN_UNDEFINED + union semun + { + int val; + struct semid_ds *buf; + unsigned short int *array; + struct seminfo *__buf; + }; + #endif + + u32 mode=1; /* 1: physical mode; 2: virtual mode. */ + int one_lock=1; + key_t key[NR_CPUS]; + int semid[NR_CPUS]; + + int create_sem(int cpu) + { + union semun arg; + char fn[MAX_FN_SIZE]; + int sid; + + sprintf(fn, PATH_FORMAT, cpu); + sprintf(fn, "%s/%s", fn, "err_type_info"); + if ((key[cpu] = ftok(fn, 'e')) == -1) { + perror("ftok"); + return -1; + } + + if (semid[cpu]!=0) + return 0; + + /* clear old semaphore */ + if ((sid = semget(key[cpu], 1, 0)) != -1) + semctl(sid, 0, IPC_RMID); + + /* get one semaphore */ + if ((semid[cpu] = semget(key[cpu], 1, IPC_CREAT | IPC_EXCL)) == -1) { + perror("semget"); + printf("Please remove semaphore with key=0x%lx, then run the tool.\n", + (u64)key[cpu]); + return -1; + } + + vbprintf("semid[%d]=0x%lx, key[%d]=%lx\n",cpu,(u64)semid[cpu],cpu, + (u64)key[cpu]); + /* initialize the semaphore to 1: */ + arg.val = 1; + if (semctl(semid[cpu], 0, SETVAL, arg) == -1) { + perror("semctl"); + return -1; + } + + return 0; + } + + static int lock(int cpu) + { + struct sembuf lock; + + lock.sem_num = cpu; + lock.sem_op = 1; + semop(semid[cpu], &lock, 1); + + return 0; + } + + static int unlock(int cpu) + { + struct sembuf unlock; + + unlock.sem_num = cpu; + unlock.sem_op = -1; + semop(semid[cpu], &unlock, 1); + + return 0; + } + + void free_sem(int cpu) + { + semctl(semid[cpu], 0, IPC_RMID); + } + + int wr_multi(char *fn, unsigned long *data, int size) + { + int fd; + char buf[MAX_BUF_SIZE]; + int ret; + + if (size==1) + sprintf(buf, "%lx", *data); + else if (size==3) + sprintf(buf, "%lx,%lx,%lx", data[0], data[1], data[2]); + else { + fprintf(stderr,"write to file with wrong size!\n"); + return -1; + } + + fd=open(fn, O_RDWR); + if (!fd) { + perror("Error:"); + return -1; + } + ret=write(fd, buf, sizeof(buf)); + close(fd); + return ret; + } + + int wr(char *fn, unsigned long data) + { + return wr_multi(fn, &data, 1); + } + + int rd(char *fn, unsigned long *data) + { + int fd; + char buf[MAX_BUF_SIZE]; + + fd=open(fn, O_RDONLY); + if (fd<0) { + perror("Error:"); + return -1; + } + read(fd, buf, MAX_BUF_SIZE); + *data=strtoul(buf, NULL, 16); + close(fd); + return 0; + } + + int rd_status(char *path, int *status) + { + char fn[MAX_FN_SIZE]; + sprintf(fn, "%s/status", path); + if (rd(fn, (u64*)status)<0) { + perror("status reading error.\n"); + return -1; + } + + return 0; + } + + int rd_capabilities(char *path, u64 *capabilities) + { + char fn[MAX_FN_SIZE]; + sprintf(fn, "%s/capabilities", path); + if (rd(fn, capabilities)<0) { + perror("capabilities reading error.\n"); + return -1; + } + + return 0; + } + + int rd_all(char *path) + { + unsigned long err_type_info, err_struct_info, err_data_buffer; + int status; + unsigned long capabilities, resources; + char fn[MAX_FN_SIZE]; + + sprintf(fn, "%s/err_type_info", path); + if (rd(fn, &err_type_info)<0) { + perror("err_type_info reading error.\n"); + return -1; + } + printf("err_type_info=%lx\n", err_type_info); + + sprintf(fn, "%s/err_struct_info", path); + if (rd(fn, &err_struct_info)<0) { + perror("err_struct_info reading error.\n"); + return -1; + } + printf("err_struct_info=%lx\n", err_struct_info); + + sprintf(fn, "%s/err_data_buffer", path); + if (rd(fn, &err_data_buffer)<0) { + perror("err_data_buffer reading error.\n"); + return -1; + } + printf("err_data_buffer=%lx\n", err_data_buffer); + + sprintf(fn, "%s/status", path); + if (rd("status", (u64*)&status)<0) { + perror("status reading error.\n"); + return -1; + } + printf("status=%d\n", status); + + sprintf(fn, "%s/capabilities", path); + if (rd(fn,&capabilities)<0) { + perror("capabilities reading error.\n"); + return -1; + } + printf("capabilities=%lx\n", capabilities); + + sprintf(fn, "%s/resources", path); + if (rd(fn, &resources)<0) { + perror("resources reading error.\n"); + return -1; + } + printf("resources=%lx\n", resources); + + return 0; + } + + int query_capabilities(char *path, err_type_info_t err_type_info, + u64 *capabilities) + { + char fn[MAX_FN_SIZE]; + err_struct_info_t err_struct_info; + err_data_buffer_t err_data_buffer; + + err_struct_info.err_struct_info=0; + memset(err_data_buffer.err_data_buffer, -1, ERR_DATA_BUFFER_SIZE*8); + + sprintf(fn, "%s/err_type_info", path); + wr(fn, err_type_info.err_type_info); + sprintf(fn, "%s/err_struct_info", path); + wr(fn, 0x0); + sprintf(fn, "%s/err_data_buffer", path); + wr_multi(fn, err_data_buffer.err_data_buffer, ERR_DATA_BUFFER_SIZE); + + // Fire pal_mc_error_inject procedure. + sprintf(fn, "%s/call_start", path); + wr(fn, mode); + + if (rd_capabilities(path, capabilities)<0) + return -1; + + return 0; + } + + int query_all_capabilities() + { + int status; + err_type_info_t err_type_info; + int err_sev, err_struct, struct_hier; + int cap=0; + u64 capabilities; + char path[MAX_FN_SIZE]; + + err_type_info.err_type_info=0; // Initial + err_type_info.err_type_info_u.mode=0; // Query mode; + err_type_info.err_type_info_u.err_inj=0; + + printf("All capabilities implemented in pal_mc_error_inject:\n"); + sprintf(path, PATH_FORMAT ,0); + for (err_sev=0;err_sev<3;err_sev++) + for (err_struct=0;err_struct<5;err_struct++) + for (struct_hier=0;struct_hier<5;struct_hier++) + { + status=-1; + capabilities=0; + err_type_info.err_type_info_u.err_sev=err_sev; + err_type_info.err_type_info_u.err_struct=err_struct; + err_type_info.err_type_info_u.struct_hier=struct_hier; + + if (query_capabilities(path, err_type_info, &capabilities)<0) + continue; + + if (rd_status(path, &status)<0) + continue; + + if (status==0) { + cap=1; + printf("For err_sev=%d, err_struct=%d, struct_hier=%d: ", + err_sev, err_struct, struct_hier); + printf("capabilities 0x%lx\n", capabilities); + } + } + if (!cap) { + printf("No capabilities supported.\n"); + return 0; + } + + return 0; + } + + int err_inject(int cpu, char *path, err_type_info_t err_type_info, + err_struct_info_t err_struct_info, + err_data_buffer_t err_data_buffer) + { + int status; + char fn[MAX_FN_SIZE]; + + log_info(cpu, "err_type_info=%lx, err_struct_info=%lx, ", + err_type_info.err_type_info, + err_struct_info.err_struct_info); + log_info(cpu,"err_data_buffer=[%lx,%lx,%lx]\n", + err_data_buffer.err_data_buffer[0], + err_data_buffer.err_data_buffer[1], + err_data_buffer.err_data_buffer[2]); + sprintf(fn, "%s/err_type_info", path); + wr(fn, err_type_info.err_type_info); + sprintf(fn, "%s/err_struct_info", path); + wr(fn, err_struct_info.err_struct_info); + sprintf(fn, "%s/err_data_buffer", path); + wr_multi(fn, err_data_buffer.err_data_buffer, ERR_DATA_BUFFER_SIZE); + + // Fire pal_mc_error_inject procedure. + sprintf(fn, "%s/call_start", path); + wr(fn,mode); + + if (rd_status(path, &status)<0) { + vbprintf("fail: read status\n"); + return -100; + } + + if (status!=0) { + log_info(cpu, "fail: status=%d\n", status); + return status; + } + + return status; + } + + static int construct_data_buf(char *path, err_type_info_t err_type_info, + err_struct_info_t err_struct_info, + err_data_buffer_t *err_data_buffer, + void *va1) + { + char fn[MAX_FN_SIZE]; + u64 virt_addr=0, phys_addr=0; + + vbprintf("va1=%lx\n", (u64)va1); + memset(&err_data_buffer->err_data_buffer_cache, 0, ERR_DATA_BUFFER_SIZE*8); + + switch (err_type_info.err_type_info_u.err_struct) { + case 1: // Cache + switch (err_struct_info.err_struct_info_cache.cl_id) { + case 1: //Virtual addr + err_data_buffer->err_data_buffer_cache.inj_addr=(u64)va1; + break; + case 2: //Phys addr + sprintf(fn, "%s/virtual_to_phys", path); + virt_addr=(u64)va1; + if (wr(fn,virt_addr)<0) + return -1; + rd(fn, &phys_addr); + err_data_buffer->err_data_buffer_cache.inj_addr=phys_addr; + break; + default: + printf("Not supported cl_id\n"); + break; + } + break; + case 2: // TLB + break; + case 3: // Register file + break; + case 4: // Bus/system interconnect + default: + printf("Not supported err_struct\n"); + break; + } + + return 0; + } + + typedef struct { + u64 cpu; + u64 loop; + u64 interval; + u64 err_type_info; + u64 err_struct_info; + u64 err_data_buffer[ERR_DATA_BUFFER_SIZE]; + } parameters_t; + + parameters_t line_para; + int para; + + static int empty_data_buffer(u64 *err_data_buffer) + { + int empty=1; + int i; + + for (i=0;i<ERR_DATA_BUFFER_SIZE; i++) + if (err_data_buffer[i]!=-1) + empty=0; + + return empty; + } + + int err_inj() + { + err_type_info_t err_type_info; + err_struct_info_t err_struct_info; + err_data_buffer_t err_data_buffer; + int count; + FILE *fp; + unsigned long cpu, loop, interval, err_type_info_conf, err_struct_info_conf; + u64 err_data_buffer_conf[ERR_DATA_BUFFER_SIZE]; + int num; + int i; + char path[MAX_FN_SIZE]; + parameters_t parameters[MAX_TASK_NUM]={}; + pid_t child_pid[MAX_TASK_NUM]; + time_t current_time; + int status; + + if (!para) { + fp=fopen("err.conf", "r"); + if (fp==NULL) { + perror("Error open err.conf"); + return -1; + } + + num=0; + while (!feof(fp)) { + char buf[256]; + memset(buf,0,256); + fgets(buf, 256, fp); + count=sscanf(buf, "%lx, %lx, %lx, %lx, %lx, %lx, %lx, %lx\n", + &cpu, &loop, &interval,&err_type_info_conf, + &err_struct_info_conf, + &err_data_buffer_conf[0], + &err_data_buffer_conf[1], + &err_data_buffer_conf[2]); + if (count!=PARA_FIELD_NUM+3) { + err_data_buffer_conf[0]=-1; + err_data_buffer_conf[1]=-1; + err_data_buffer_conf[2]=-1; + count=sscanf(buf, "%lx, %lx, %lx, %lx, %lx\n", + &cpu, &loop, &interval,&err_type_info_conf, + &err_struct_info_conf); + if (count!=PARA_FIELD_NUM) + continue; + } + + parameters[num].cpu=cpu; + parameters[num].loop=loop; + parameters[num].interval= interval>MIN_INTERVAL + ?interval:MIN_INTERVAL; + parameters[num].err_type_info=err_type_info_conf; + parameters[num].err_struct_info=err_struct_info_conf; + memcpy(parameters[num++].err_data_buffer, + err_data_buffer_conf,ERR_DATA_BUFFER_SIZE*8) ; + + if (num>=MAX_TASK_NUM) + break; + } + } + else { + parameters[0].cpu=line_para.cpu; + parameters[0].loop=line_para.loop; + parameters[0].interval= line_para.interval>MIN_INTERVAL + ?line_para.interval:MIN_INTERVAL; + parameters[0].err_type_info=line_para.err_type_info; + parameters[0].err_struct_info=line_para.err_struct_info; + memcpy(parameters[0].err_data_buffer, + line_para.err_data_buffer,ERR_DATA_BUFFER_SIZE*8) ; + + num=1; + } + + /* Create semaphore: If one_lock, one semaphore for all processors. + Otherwise, one semaphore for each processor. */ + if (one_lock) { + if (create_sem(0)) { + printf("Can not create semaphore...exit\n"); + free_sem(0); + return -1; + } + } + else { + for (i=0;i<num;i++) { + if (create_sem(parameters[i].cpu)) { + printf("Can not create semaphore for cpu%d...exit\n",i); + free_sem(parameters[num].cpu); + return -1; + } + } + } + + /* Create a shm segment which will be used to inject/consume errors on.*/ + if (create_shm()==-1) { + printf("Error to create shm...exit\n"); + return -1; + } + + for (i=0;i<num;i++) { + pid_t pid; + + current_time=time(NULL); + log_info(parameters[i].cpu, "\nBegine at %s", ctime(¤t_time)); + log_info(parameters[i].cpu, "Configurations:\n"); + log_info(parameters[i].cpu,"On cpu%ld: loop=%lx, interval=%lx(s)", + parameters[i].cpu, + parameters[i].loop, + parameters[i].interval); + log_info(parameters[i].cpu," err_type_info=%lx,err_struct_info=%lx\n", + parameters[i].err_type_info, + parameters[i].err_struct_info); + + sprintf(path, PATH_FORMAT, (int)parameters[i].cpu); + err_type_info.err_type_info=parameters[i].err_type_info; + err_struct_info.err_struct_info=parameters[i].err_struct_info; + memcpy(err_data_buffer.err_data_buffer, + parameters[i].err_data_buffer, + ERR_DATA_BUFFER_SIZE*8); + + pid=fork(); + if (pid==0) { + unsigned long mask[MASK_SIZE]; + int j, k; + + void *va1, *va2; + + /* Allocate two memory areas va1 and va2 in shm */ + va1=shmaddr+parameters[i].cpu*PAGE_SIZE; + va2=shmaddr+parameters[i].cpu*PAGE_SIZE+PAGE_SIZE; + + vbprintf("va1=%lx, va2=%lx\n", (u64)va1, (u64)va2); + memset(va1, 0x1, PAGE_SIZE); + memset(va2, 0x2, PAGE_SIZE); + + if (empty_data_buffer(err_data_buffer.err_data_buffer)) + /* If not specified yet, construct data buffer + * with va1 + */ + construct_data_buf(path, err_type_info, + err_struct_info, &err_data_buffer,va1); + + for (j=0;j<MASK_SIZE;j++) + mask[j]=0; + + cpu=parameters[i].cpu; + k = cpu%64; + j = cpu/64; + mask[j] = 1UL << k; + + if (sched_setaffinity(0, MASK_SIZE*8, mask)==-1) { + perror("Error sched_setaffinity:"); + return -1; + } + + for (j=0; j<parameters[i].loop; j++) { + log_info(parameters[i].cpu,"Injection "); + log_info(parameters[i].cpu,"on cpu%ld: #%d/%ld ", + + parameters[i].cpu,j+1, parameters[i].loop); + + /* Hold the lock */ + if (one_lock) + lock(0); + else + /* Hold lock on this cpu */ + lock(parameters[i].cpu); + + if ((status=err_inject(parameters[i].cpu, + path, err_type_info, + err_struct_info, err_data_buffer)) + ==0) { + /* consume the error for "inject only"*/ + memcpy(va2, va1, PAGE_SIZE); + memcpy(va1, va2, PAGE_SIZE); + log_info(parameters[i].cpu, + "successful\n"); + } + else { + log_info(parameters[i].cpu,"fail:"); + log_info(parameters[i].cpu, + "status=%d\n", status); + unlock(parameters[i].cpu); + break; + } + if (one_lock) + /* Release the lock */ + unlock(0); + /* Release lock on this cpu */ + else + unlock(parameters[i].cpu); + + if (j < parameters[i].loop-1) + sleep(parameters[i].interval); + } + current_time=time(NULL); + log_info(parameters[i].cpu, "Done at %s", ctime(¤t_time)); + return 0; + } + else if (pid<0) { + perror("Error fork:"); + continue; + } + child_pid[i]=pid; + } + for (i=0;i<num;i++) + waitpid(child_pid[i], NULL, 0); + + if (one_lock) + free_sem(0); + else + for (i=0;i<num;i++) + free_sem(parameters[i].cpu); + + printf("All done.\n"); + + return 0; + } + + void help() + { + printf("err_inject_tool:\n"); + printf("\t-q: query all capabilities. default: off\n"); + printf("\t-m: procedure mode. 1: physical 2: virtual. default: 1\n"); + printf("\t-i: inject errors. default: off\n"); + printf("\t-l: one lock per cpu. default: one lock for all\n"); + printf("\t-e: error parameters:\n"); + printf("\t\tcpu,loop,interval,err_type_info,err_struct_info[,err_data_buffer[0],err_data_buffer[1],err_data_buffer[2]]\n"); + printf("\t\t cpu: logical cpu number the error will be inject in.\n"); + printf("\t\t loop: times the error will be injected.\n"); + printf("\t\t interval: In second. every so often one error is injected.\n"); + printf("\t\t err_type_info, err_struct_info: PAL parameters.\n"); + printf("\t\t err_data_buffer: PAL parameter. Optional. If not present,\n"); + printf("\t\t it's constructed by tool automatically. Be\n"); + printf("\t\t careful to provide err_data_buffer and make\n"); + printf("\t\t sure it's working with the environment.\n"); + printf("\t Note:no space between error parameters.\n"); + printf("\t default: Take error parameters from err.conf instead of command line.\n"); + printf("\t-v: verbose. default: off\n"); + printf("\t-h: help\n\n"); + printf("The tool will take err.conf file as "); + printf("input to inject single or multiple errors "); + printf("on one or multiple cpus in parallel.\n"); + } + + int main(int argc, char **argv) + { + char c; + int do_err_inj=0; + int do_query_all=0; + int count; + u32 m; + + /* Default one lock for all cpu's */ + one_lock=1; + while ((c = getopt(argc, argv, "m:iqvhle:")) != EOF) + switch (c) { + case 'm': /* Procedure mode. 1: phys 2: virt */ + count=sscanf(optarg, "%x", &m); + if (count!=1 || (m!=1 && m!=2)) { + printf("Wrong mode number.\n"); + help(); + return -1; + } + mode=m; + break; + case 'i': /* Inject errors */ + do_err_inj=1; + break; + case 'q': /* Query */ + do_query_all=1; + break; + case 'v': /* Verbose */ + verbose=1; + break; + case 'l': /* One lock per cpu */ + one_lock=0; + break; + case 'e': /* error arguments */ + /* Take parameters: + * #cpu, loop, interval, err_type_info, err_struct_info[, err_data_buffer] + * err_data_buffer is optional. Recommend not to specify + * err_data_buffer. Better to use tool to generate it. + */ + count=sscanf(optarg, + "%lx, %lx, %lx, %lx, %lx, %lx, %lx, %lx\n", + &line_para.cpu, + &line_para.loop, + &line_para.interval, + &line_para.err_type_info, + &line_para.err_struct_info, + &line_para.err_data_buffer[0], + &line_para.err_data_buffer[1], + &line_para.err_data_buffer[2]); + if (count!=PARA_FIELD_NUM+3) { + line_para.err_data_buffer[0]=-1, + line_para.err_data_buffer[1]=-1, + line_para.err_data_buffer[2]=-1; + count=sscanf(optarg, "%lx, %lx, %lx, %lx, %lx\n", + &line_para.cpu, + &line_para.loop, + &line_para.interval, + &line_para.err_type_info, + &line_para.err_struct_info); + if (count!=PARA_FIELD_NUM) { + printf("Wrong error arguments.\n"); + help(); + return -1; + } + } + para=1; + break; + continue; + break; + case 'h': + help(); + return 0; + default: + break; + } + + if (do_query_all) + query_all_capabilities(); + if (do_err_inj) + err_inj(); + + if (!do_query_all && !do_err_inj) + help(); + + return 0; + } diff --git a/Documentation/ia64/features.rst b/Documentation/ia64/features.rst new file mode 100644 index 000000000..d7226fdcf --- /dev/null +++ b/Documentation/ia64/features.rst @@ -0,0 +1,3 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. kernel-feat:: $srctree/Documentation/features ia64 diff --git a/Documentation/ia64/fsys.rst b/Documentation/ia64/fsys.rst new file mode 100644 index 000000000..a702d2cc9 --- /dev/null +++ b/Documentation/ia64/fsys.rst @@ -0,0 +1,303 @@ +=================================== +Light-weight System Calls for IA-64 +=================================== + + Started: 13-Jan-2003 + + Last update: 27-Sep-2003 + + David Mosberger-Tang + <davidm@hpl.hp.com> + +Using the "epc" instruction effectively introduces a new mode of +execution to the ia64 linux kernel. We call this mode the +"fsys-mode". To recap, the normal states of execution are: + + - kernel mode: + Both the register stack and the memory stack have been + switched over to kernel memory. The user-level state is saved + in a pt-regs structure at the top of the kernel memory stack. + + - user mode: + Both the register stack and the kernel stack are in + user memory. The user-level state is contained in the + CPU registers. + + - bank 0 interruption-handling mode: + This is the non-interruptible state which all + interruption-handlers start execution in. The user-level + state remains in the CPU registers and some kernel state may + be stored in bank 0 of registers r16-r31. + +In contrast, fsys-mode has the following special properties: + + - execution is at privilege level 0 (most-privileged) + + - CPU registers may contain a mixture of user-level and kernel-level + state (it is the responsibility of the kernel to ensure that no + security-sensitive kernel-level state is leaked back to + user-level) + + - execution is interruptible and preemptible (an fsys-mode handler + can disable interrupts and avoid all other interruption-sources + to avoid preemption) + + - neither the memory-stack nor the register-stack can be trusted while + in fsys-mode (they point to the user-level stacks, which may + be invalid, or completely bogus addresses) + +In summary, fsys-mode is much more similar to running in user-mode +than it is to running in kernel-mode. Of course, given that the +privilege level is at level 0, this means that fsys-mode requires some +care (see below). + + +How to tell fsys-mode +===================== + +Linux operates in fsys-mode when (a) the privilege level is 0 (most +privileged) and (b) the stacks have NOT been switched to kernel memory +yet. For convenience, the header file <asm-ia64/ptrace.h> provides +three macros:: + + user_mode(regs) + user_stack(task,regs) + fsys_mode(task,regs) + +The "regs" argument is a pointer to a pt_regs structure. The "task" +argument is a pointer to the task structure to which the "regs" +pointer belongs to. user_mode() returns TRUE if the CPU state pointed +to by "regs" was executing in user mode (privilege level 3). +user_stack() returns TRUE if the state pointed to by "regs" was +executing on the user-level stack(s). Finally, fsys_mode() returns +TRUE if the CPU state pointed to by "regs" was executing in fsys-mode. +The fsys_mode() macro is equivalent to the expression:: + + !user_mode(regs) && user_stack(task,regs) + +How to write an fsyscall handler +================================ + +The file arch/ia64/kernel/fsys.S contains a table of fsyscall-handlers +(fsyscall_table). This table contains one entry for each system call. +By default, a system call is handled by fsys_fallback_syscall(). This +routine takes care of entering (full) kernel mode and calling the +normal Linux system call handler. For performance-critical system +calls, it is possible to write a hand-tuned fsyscall_handler. For +example, fsys.S contains fsys_getpid(), which is a hand-tuned version +of the getpid() system call. + +The entry and exit-state of an fsyscall handler is as follows: + +Machine state on entry to fsyscall handler +------------------------------------------ + + ========= =============================================================== + r10 0 + r11 saved ar.pfs (a user-level value) + r15 system call number + r16 "current" task pointer (in normal kernel-mode, this is in r13) + r32-r39 system call arguments + b6 return address (a user-level value) + ar.pfs previous frame-state (a user-level value) + PSR.be cleared to zero (i.e., little-endian byte order is in effect) + - all other registers may contain values passed in from user-mode + ========= =============================================================== + +Required machine state on exit to fsyscall handler +-------------------------------------------------- + + ========= =========================================================== + r11 saved ar.pfs (as passed into the fsyscall handler) + r15 system call number (as passed into the fsyscall handler) + r32-r39 system call arguments (as passed into the fsyscall handler) + b6 return address (as passed into the fsyscall handler) + ar.pfs previous frame-state (as passed into the fsyscall handler) + ========= =========================================================== + +Fsyscall handlers can execute with very little overhead, but with that +speed comes a set of restrictions: + + * Fsyscall-handlers MUST check for any pending work in the flags + member of the thread-info structure and if any of the + TIF_ALLWORK_MASK flags are set, the handler needs to fall back on + doing a full system call (by calling fsys_fallback_syscall). + + * Fsyscall-handlers MUST preserve incoming arguments (r32-r39, r11, + r15, b6, and ar.pfs) because they will be needed in case of a + system call restart. Of course, all "preserved" registers also + must be preserved, in accordance to the normal calling conventions. + + * Fsyscall-handlers MUST check argument registers for containing a + NaT value before using them in any way that could trigger a + NaT-consumption fault. If a system call argument is found to + contain a NaT value, an fsyscall-handler may return immediately + with r8=EINVAL, r10=-1. + + * Fsyscall-handlers MUST NOT use the "alloc" instruction or perform + any other operation that would trigger mandatory RSE + (register-stack engine) traffic. + + * Fsyscall-handlers MUST NOT write to any stacked registers because + it is not safe to assume that user-level called a handler with the + proper number of arguments. + + * Fsyscall-handlers need to be careful when accessing per-CPU variables: + unless proper safe-guards are taken (e.g., interruptions are avoided), + execution may be pre-empted and resumed on another CPU at any given + time. + + * Fsyscall-handlers must be careful not to leak sensitive kernel' + information back to user-level. In particular, before returning to + user-level, care needs to be taken to clear any scratch registers + that could contain sensitive information (note that the current + task pointer is not considered sensitive: it's already exposed + through ar.k6). + + * Fsyscall-handlers MUST NOT access user-memory without first + validating access-permission (this can be done typically via + probe.r.fault and/or probe.w.fault) and without guarding against + memory access exceptions (this can be done with the EX() macros + defined by asmmacro.h). + +The above restrictions may seem draconian, but remember that it's +possible to trade off some of the restrictions by paying a slightly +higher overhead. For example, if an fsyscall-handler could benefit +from the shadow register bank, it could temporarily disable PSR.i and +PSR.ic, switch to bank 0 (bsw.0) and then use the shadow registers as +needed. In other words, following the above rules yields extremely +fast system call execution (while fully preserving system call +semantics), but there is also a lot of flexibility in handling more +complicated cases. + +Signal handling +=============== + +The delivery of (asynchronous) signals must be delayed until fsys-mode +is exited. This is accomplished with the help of the lower-privilege +transfer trap: arch/ia64/kernel/process.c:do_notify_resume_user() +checks whether the interrupted task was in fsys-mode and, if so, sets +PSR.lp and returns immediately. When fsys-mode is exited via the +"br.ret" instruction that lowers the privilege level, a trap will +occur. The trap handler clears PSR.lp again and returns immediately. +The kernel exit path then checks for and delivers any pending signals. + +PSR Handling +============ + +The "epc" instruction doesn't change the contents of PSR at all. This +is in contrast to a regular interruption, which clears almost all +bits. Because of that, some care needs to be taken to ensure things +work as expected. The following discussion describes how each PSR bit +is handled. + +======= ======================================================================= +PSR.be Cleared when entering fsys-mode. A srlz.d instruction is used + to ensure the CPU is in little-endian mode before the first + load/store instruction is executed. PSR.be is normally NOT + restored upon return from an fsys-mode handler. In other + words, user-level code must not rely on PSR.be being preserved + across a system call. +PSR.up Unchanged. +PSR.ac Unchanged. +PSR.mfl Unchanged. Note: fsys-mode handlers must not write-registers! +PSR.mfh Unchanged. Note: fsys-mode handlers must not write-registers! +PSR.ic Unchanged. Note: fsys-mode handlers can clear the bit, if needed. +PSR.i Unchanged. Note: fsys-mode handlers can clear the bit, if needed. +PSR.pk Unchanged. +PSR.dt Unchanged. +PSR.dfl Unchanged. Note: fsys-mode handlers must not write-registers! +PSR.dfh Unchanged. Note: fsys-mode handlers must not write-registers! +PSR.sp Unchanged. +PSR.pp Unchanged. +PSR.di Unchanged. +PSR.si Unchanged. +PSR.db Unchanged. The kernel prevents user-level from setting a hardware + breakpoint that triggers at any privilege level other than + 3 (user-mode). +PSR.lp Unchanged. +PSR.tb Lazy redirect. If a taken-branch trap occurs while in + fsys-mode, the trap-handler modifies the saved machine state + such that execution resumes in the gate page at + syscall_via_break(), with privilege level 3. Note: the + taken branch would occur on the branch invoking the + fsyscall-handler, at which point, by definition, a syscall + restart is still safe. If the system call number is invalid, + the fsys-mode handler will return directly to user-level. This + return will trigger a taken-branch trap, but since the trap is + taken _after_ restoring the privilege level, the CPU has already + left fsys-mode, so no special treatment is needed. +PSR.rt Unchanged. +PSR.cpl Cleared to 0. +PSR.is Unchanged (guaranteed to be 0 on entry to the gate page). +PSR.mc Unchanged. +PSR.it Unchanged (guaranteed to be 1). +PSR.id Unchanged. Note: the ia64 linux kernel never sets this bit. +PSR.da Unchanged. Note: the ia64 linux kernel never sets this bit. +PSR.dd Unchanged. Note: the ia64 linux kernel never sets this bit. +PSR.ss Lazy redirect. If set, "epc" will cause a Single Step Trap to + be taken. The trap handler then modifies the saved machine + state such that execution resumes in the gate page at + syscall_via_break(), with privilege level 3. +PSR.ri Unchanged. +PSR.ed Unchanged. Note: This bit could only have an effect if an fsys-mode + handler performed a speculative load that gets NaTted. If so, this + would be the normal & expected behavior, so no special treatment is + needed. +PSR.bn Unchanged. Note: fsys-mode handlers may clear the bit, if needed. + Doing so requires clearing PSR.i and PSR.ic as well. +PSR.ia Unchanged. Note: the ia64 linux kernel never sets this bit. +======= ======================================================================= + +Using fast system calls +======================= + +To use fast system calls, userspace applications need simply call +__kernel_syscall_via_epc(). For example + +-- example fgettimeofday() call -- + +-- fgettimeofday.S -- + +:: + + #include <asm/asmmacro.h> + + GLOBAL_ENTRY(fgettimeofday) + .prologue + .save ar.pfs, r11 + mov r11 = ar.pfs + .body + + mov r2 = 0xa000000000020660;; // gate address + // found by inspection of System.map for the + // __kernel_syscall_via_epc() function. See + // below for how to do this for real. + + mov b7 = r2 + mov r15 = 1087 // gettimeofday syscall + ;; + br.call.sptk.many b6 = b7 + ;; + + .restore sp + + mov ar.pfs = r11 + br.ret.sptk.many rp;; // return to caller + END(fgettimeofday) + +-- end fgettimeofday.S -- + +In reality, getting the gate address is accomplished by two extra +values passed via the ELF auxiliary vector (include/asm-ia64/elf.h) + + * AT_SYSINFO : is the address of __kernel_syscall_via_epc() + * AT_SYSINFO_EHDR : is the address of the kernel gate ELF DSO + +The ELF DSO is a pre-linked library that is mapped in by the kernel at +the gate page. It is a proper ELF shared object so, with a dynamic +loader that recognises the library, you should be able to make calls to +the exported functions within it as with any other shared library. +AT_SYSINFO points into the kernel DSO at the +__kernel_syscall_via_epc() function for historical reasons (it was +used before the kernel DSO) and as a convenience. diff --git a/Documentation/ia64/ia64.rst b/Documentation/ia64/ia64.rst new file mode 100644 index 000000000..b725019a9 --- /dev/null +++ b/Documentation/ia64/ia64.rst @@ -0,0 +1,49 @@ +=========================================== +Linux kernel release for the IA-64 Platform +=========================================== + + These are the release notes for Linux since version 2.4 for IA-64 + platform. This document provides information specific to IA-64 + ONLY, to get additional information about the Linux kernel also + read the original Linux README provided with the kernel. + +Installing the Kernel +===================== + + - IA-64 kernel installation is the same as the other platforms, see + original README for details. + + +Software Requirements +===================== + + Compiling and running this kernel requires an IA-64 compliant GCC + compiler. And various software packages also compiled with an + IA-64 compliant GCC compiler. + + +Configuring the Kernel +====================== + + Configuration is the same, see original README for details. + + +Compiling the Kernel: + + - Compiling this kernel doesn't differ from other platform so read + the original README for details BUT make sure you have an IA-64 + compliant GCC compiler. + +IA-64 Specifics +=============== + + - General issues: + + * Hardly any performance tuning has been done. Obvious targets + include the library routines (IP checksum, etc.). Less + obvious targets include making sure we don't flush the TLB + needlessly, etc. + + * SMP locks cleanup/optimization + + * IA32 support. Currently experimental. It mostly works. diff --git a/Documentation/ia64/index.rst b/Documentation/ia64/index.rst new file mode 100644 index 000000000..761f2154d --- /dev/null +++ b/Documentation/ia64/index.rst @@ -0,0 +1,19 @@ +.. SPDX-License-Identifier: GPL-2.0 + +================== +IA-64 Architecture +================== + +.. toctree:: + :maxdepth: 1 + + ia64 + aliasing + efirtc + err_inject + fsys + irq-redir + mca + serial + + features diff --git a/Documentation/ia64/irq-redir.rst b/Documentation/ia64/irq-redir.rst new file mode 100644 index 000000000..6bbbbe4f7 --- /dev/null +++ b/Documentation/ia64/irq-redir.rst @@ -0,0 +1,80 @@ +============================== +IRQ affinity on IA64 platforms +============================== + +07.01.2002, Erich Focht <efocht@ess.nec.de> + + +By writing to /proc/irq/IRQ#/smp_affinity the interrupt routing can be +controlled. The behavior on IA64 platforms is slightly different from +that described in Documentation/core-api/irq/irq-affinity.rst for i386 systems. + +Because of the usage of SAPIC mode and physical destination mode the +IRQ target is one particular CPU and cannot be a mask of several +CPUs. Only the first non-zero bit is taken into account. + + +Usage examples +============== + +The target CPU has to be specified as a hexadecimal CPU mask. The +first non-zero bit is the selected CPU. This format has been kept for +compatibility reasons with i386. + +Set the delivery mode of interrupt 41 to fixed and route the +interrupts to CPU #3 (logical CPU number) (2^3=0x08):: + + echo "8" >/proc/irq/41/smp_affinity + +Set the default route for IRQ number 41 to CPU 6 in lowest priority +delivery mode (redirectable):: + + echo "r 40" >/proc/irq/41/smp_affinity + +The output of the command:: + + cat /proc/irq/IRQ#/smp_affinity + +gives the target CPU mask for the specified interrupt vector. If the CPU +mask is preceded by the character "r", the interrupt is redirectable +(i.e. lowest priority mode routing is used), otherwise its route is +fixed. + + + +Initialization and default behavior +=================================== + +If the platform features IRQ redirection (info provided by SAL) all +IO-SAPIC interrupts are initialized with CPU#0 as their default target +and the routing is the so called "lowest priority mode" (actually +fixed SAPIC mode with hint). The XTP chipset registers are used as hints +for the IRQ routing. Currently in Linux XTP registers can have three +values: + + - minimal for an idle task, + - normal if any other task runs, + - maximal if the CPU is going to be switched off. + +The IRQ is routed to the CPU with lowest XTP register value, the +search begins at the default CPU. Therefore most of the interrupts +will be handled by CPU #0. + +If the platform doesn't feature interrupt redirection IOSAPIC fixed +routing is used. The target CPUs are distributed in a round robin +manner. IRQs will be routed only to the selected target CPUs. Check +with:: + + cat /proc/interrupts + + + +Comments +======== + +On large (multi-node) systems it is recommended to route the IRQs to +the node to which the corresponding device is connected. +For systems like the NEC AzusA we get IRQ node-affinity for free. This +is because usually the chipsets on each node redirect the interrupts +only to their own CPUs (as they cannot see the XTP registers on the +other nodes). diff --git a/Documentation/ia64/mca.rst b/Documentation/ia64/mca.rst new file mode 100644 index 000000000..08270bba4 --- /dev/null +++ b/Documentation/ia64/mca.rst @@ -0,0 +1,198 @@ +============================================================= +An ad-hoc collection of notes on IA64 MCA and INIT processing +============================================================= + +Feel free to update it with notes about any area that is not clear. + +--- + +MCA/INIT are completely asynchronous. They can occur at any time, when +the OS is in any state. Including when one of the cpus is already +holding a spinlock. Trying to get any lock from MCA/INIT state is +asking for deadlock. Also the state of structures that are protected +by locks is indeterminate, including linked lists. + +--- + +The complicated ia64 MCA process. All of this is mandated by Intel's +specification for ia64 SAL, error recovery and unwind, it is not as +if we have a choice here. + +* MCA occurs on one cpu, usually due to a double bit memory error. + This is the monarch cpu. + +* SAL sends an MCA rendezvous interrupt (which is a normal interrupt) + to all the other cpus, the slaves. + +* Slave cpus that receive the MCA interrupt call down into SAL, they + end up spinning disabled while the MCA is being serviced. + +* If any slave cpu was already spinning disabled when the MCA occurred + then it cannot service the MCA interrupt. SAL waits ~20 seconds then + sends an unmaskable INIT event to the slave cpus that have not + already rendezvoused. + +* Because MCA/INIT can be delivered at any time, including when the cpu + is down in PAL in physical mode, the registers at the time of the + event are _completely_ undefined. In particular the MCA/INIT + handlers cannot rely on the thread pointer, PAL physical mode can + (and does) modify TP. It is allowed to do that as long as it resets + TP on return. However MCA/INIT events expose us to these PAL + internal TP changes. Hence curr_task(). + +* If an MCA/INIT event occurs while the kernel was running (not user + space) and the kernel has called PAL then the MCA/INIT handler cannot + assume that the kernel stack is in a fit state to be used. Mainly + because PAL may or may not maintain the stack pointer internally. + Because the MCA/INIT handlers cannot trust the kernel stack, they + have to use their own, per-cpu stacks. The MCA/INIT stacks are + preformatted with just enough task state to let the relevant handlers + do their job. + +* Unlike most other architectures, the ia64 struct task is embedded in + the kernel stack[1]. So switching to a new kernel stack means that + we switch to a new task as well. Because various bits of the kernel + assume that current points into the struct task, switching to a new + stack also means a new value for current. + +* Once all slaves have rendezvoused and are spinning disabled, the + monarch is entered. The monarch now tries to diagnose the problem + and decide if it can recover or not. + +* Part of the monarch's job is to look at the state of all the other + tasks. The only way to do that on ia64 is to call the unwinder, + as mandated by Intel. + +* The starting point for the unwind depends on whether a task is + running or not. That is, whether it is on a cpu or is blocked. The + monarch has to determine whether or not a task is on a cpu before it + knows how to start unwinding it. The tasks that received an MCA or + INIT event are no longer running, they have been converted to blocked + tasks. But (and its a big but), the cpus that received the MCA + rendezvous interrupt are still running on their normal kernel stacks! + +* To distinguish between these two cases, the monarch must know which + tasks are on a cpu and which are not. Hence each slave cpu that + switches to an MCA/INIT stack, registers its new stack using + set_curr_task(), so the monarch can tell that the _original_ task is + no longer running on that cpu. That gives us a decent chance of + getting a valid backtrace of the _original_ task. + +* MCA/INIT can be nested, to a depth of 2 on any cpu. In the case of a + nested error, we want diagnostics on the MCA/INIT handler that + failed, not on the task that was originally running. Again this + requires set_curr_task() so the MCA/INIT handlers can register their + own stack as running on that cpu. Then a recursive error gets a + trace of the failing handler's "task". + +[1] + My (Keith Owens) original design called for ia64 to separate its + struct task and the kernel stacks. Then the MCA/INIT data would be + chained stacks like i386 interrupt stacks. But that required + radical surgery on the rest of ia64, plus extra hard wired TLB + entries with its associated performance degradation. David + Mosberger vetoed that approach. Which meant that separate kernel + stacks meant separate "tasks" for the MCA/INIT handlers. + +--- + +INIT is less complicated than MCA. Pressing the nmi button or using +the equivalent command on the management console sends INIT to all +cpus. SAL picks one of the cpus as the monarch and the rest are +slaves. All the OS INIT handlers are entered at approximately the same +time. The OS monarch prints the state of all tasks and returns, after +which the slaves return and the system resumes. + +At least that is what is supposed to happen. Alas there are broken +versions of SAL out there. Some drive all the cpus as monarchs. Some +drive them all as slaves. Some drive one cpu as monarch, wait for that +cpu to return from the OS then drive the rest as slaves. Some versions +of SAL cannot even cope with returning from the OS, they spin inside +SAL on resume. The OS INIT code has workarounds for some of these +broken SAL symptoms, but some simply cannot be fixed from the OS side. + +--- + +The scheduler hooks used by ia64 (curr_task, set_curr_task) are layer +violations. Unfortunately MCA/INIT start off as massive layer +violations (can occur at _any_ time) and they build from there. + +At least ia64 makes an attempt at recovering from hardware errors, but +it is a difficult problem because of the asynchronous nature of these +errors. When processing an unmaskable interrupt we sometimes need +special code to cope with our inability to take any locks. + +--- + +How is ia64 MCA/INIT different from x86 NMI? + +* x86 NMI typically gets delivered to one cpu. MCA/INIT gets sent to + all cpus. + +* x86 NMI cannot be nested. MCA/INIT can be nested, to a depth of 2 + per cpu. + +* x86 has a separate struct task which points to one of multiple kernel + stacks. ia64 has the struct task embedded in the single kernel + stack, so switching stack means switching task. + +* x86 does not call the BIOS so the NMI handler does not have to worry + about any registers having changed. MCA/INIT can occur while the cpu + is in PAL in physical mode, with undefined registers and an undefined + kernel stack. + +* i386 backtrace is not very sensitive to whether a process is running + or not. ia64 unwind is very, very sensitive to whether a process is + running or not. + +--- + +What happens when MCA/INIT is delivered what a cpu is running user +space code? + +The user mode registers are stored in the RSE area of the MCA/INIT on +entry to the OS and are restored from there on return to SAL, so user +mode registers are preserved across a recoverable MCA/INIT. Since the +OS has no idea what unwind data is available for the user space stack, +MCA/INIT never tries to backtrace user space. Which means that the OS +does not bother making the user space process look like a blocked task, +i.e. the OS does not copy pt_regs and switch_stack to the user space +stack. Also the OS has no idea how big the user space RSE and memory +stacks are, which makes it too risky to copy the saved state to a user +mode stack. + +--- + +How do we get a backtrace on the tasks that were running when MCA/INIT +was delivered? + +mca.c:::ia64_mca_modify_original_stack(). That identifies and +verifies the original kernel stack, copies the dirty registers from +the MCA/INIT stack's RSE to the original stack's RSE, copies the +skeleton struct pt_regs and switch_stack to the original stack, fills +in the skeleton structures from the PAL minstate area and updates the +original stack's thread.ksp. That makes the original stack look +exactly like any other blocked task, i.e. it now appears to be +sleeping. To get a backtrace, just start with thread.ksp for the +original task and unwind like any other sleeping task. + +--- + +How do we identify the tasks that were running when MCA/INIT was +delivered? + +If the previous task has been verified and converted to a blocked +state, then sos->prev_task on the MCA/INIT stack is updated to point to +the previous task. You can look at that field in dumps or debuggers. +To help distinguish between the handler and the original tasks, +handlers have _TIF_MCA_INIT set in thread_info.flags. + +The sos data is always in the MCA/INIT handler stack, at offset +MCA_SOS_OFFSET. You can get that value from mca_asm.h or calculate it +as KERNEL_STACK_SIZE - sizeof(struct pt_regs) - sizeof(struct +ia64_sal_os_state), with 16 byte alignment for all structures. + +Also the comm field of the MCA/INIT task is modified to include the pid +of the original task, for humans to use. For example, a comm field of +'MCA 12159' means that pid 12159 was running when the MCA was +delivered. diff --git a/Documentation/ia64/serial.rst b/Documentation/ia64/serial.rst new file mode 100644 index 000000000..1de70c305 --- /dev/null +++ b/Documentation/ia64/serial.rst @@ -0,0 +1,165 @@ +============== +Serial Devices +============== + +Serial Device Naming +==================== + + As of 2.6.10, serial devices on ia64 are named based on the + order of ACPI and PCI enumeration. The first device in the + ACPI namespace (if any) becomes /dev/ttyS0, the second becomes + /dev/ttyS1, etc., and PCI devices are named sequentially + starting after the ACPI devices. + + Prior to 2.6.10, there were confusing exceptions to this: + + - Firmware on some machines (mostly from HP) provides an HCDP + table[1] that tells the kernel about devices that can be used + as a serial console. If the user specified "console=ttyS0" + or the EFI ConOut path contained only UART devices, the + kernel registered the device described by the HCDP as + /dev/ttyS0. + + - If there was no HCDP, we assumed there were UARTs at the + legacy COM port addresses (I/O ports 0x3f8 and 0x2f8), so + the kernel registered those as /dev/ttyS0 and /dev/ttyS1. + + Any additional ACPI or PCI devices were registered sequentially + after /dev/ttyS0 as they were discovered. + + With an HCDP, device names changed depending on EFI configuration + and "console=" arguments. Without an HCDP, device names didn't + change, but we registered devices that might not really exist. + + For example, an HP rx1600 with a single built-in serial port + (described in the ACPI namespace) plus an MP[2] (a PCI device) has + these ports: + + ========== ========== ============ ============ ======= + Type MMIO pre-2.6.10 pre-2.6.10 2.6.10+ + address + (EFI console (EFI console + on builtin) on MP port) + ========== ========== ============ ============ ======= + builtin 0xff5e0000 ttyS0 ttyS1 ttyS0 + MP UPS 0xf8031000 ttyS1 ttyS2 ttyS1 + MP Console 0xf8030000 ttyS2 ttyS0 ttyS2 + MP 2 0xf8030010 ttyS3 ttyS3 ttyS3 + MP 3 0xf8030038 ttyS4 ttyS4 ttyS4 + ========== ========== ============ ============ ======= + +Console Selection +================= + + EFI knows what your console devices are, but it doesn't tell the + kernel quite enough to actually locate them. The DIG64 HCDP + table[1] does tell the kernel where potential serial console + devices are, but not all firmware supplies it. Also, EFI supports + multiple simultaneous consoles and doesn't tell the kernel which + should be the "primary" one. + + So how do you tell Linux which console device to use? + + - If your firmware supplies the HCDP, it is simplest to + configure EFI with a single device (either a UART or a VGA + card) as the console. Then you don't need to tell Linux + anything; the kernel will automatically use the EFI console. + + (This works only in 2.6.6 or later; prior to that you had + to specify "console=ttyS0" to get a serial console.) + + - Without an HCDP, Linux defaults to a VGA console unless you + specify a "console=" argument. + + NOTE: Don't assume that a serial console device will be /dev/ttyS0. + It might be ttyS1, ttyS2, etc. Make sure you have the appropriate + entries in /etc/inittab (for getty) and /etc/securetty (to allow + root login). + +Early Serial Console +==================== + + The kernel can't start using a serial console until it knows where + the device lives. Normally this happens when the driver enumerates + all the serial devices, which can happen a minute or more after the + kernel starts booting. + + 2.6.10 and later kernels have an "early uart" driver that works + very early in the boot process. The kernel will automatically use + this if the user supplies an argument like "console=uart,io,0x3f8", + or if the EFI console path contains only a UART device and the + firmware supplies an HCDP. + +Troubleshooting Serial Console Problems +======================================= + + No kernel output after elilo prints "Uncompressing Linux... done": + + - You specified "console=ttyS0" but Linux changed the device + to which ttyS0 refers. Configure exactly one EFI console + device[3] and remove the "console=" option. + + - The EFI console path contains both a VGA device and a UART. + EFI and elilo use both, but Linux defaults to VGA. Remove + the VGA device from the EFI console path[3]. + + - Multiple UARTs selected as EFI console devices. EFI and + elilo use all selected devices, but Linux uses only one. + Make sure only one UART is selected in the EFI console + path[3]. + + - You're connected to an HP MP port[2] but have a non-MP UART + selected as EFI console device. EFI uses the MP as a + console device even when it isn't explicitly selected. + Either move the console cable to the non-MP UART, or change + the EFI console path[3] to the MP UART. + + Long pause (60+ seconds) between "Uncompressing Linux... done" and + start of kernel output: + + - No early console because you used "console=ttyS<n>". Remove + the "console=" option if your firmware supplies an HCDP. + + - If you don't have an HCDP, the kernel doesn't know where + your console lives until the driver discovers serial + devices. Use "console=uart,io,0x3f8" (or appropriate + address for your machine). + + Kernel and init script output works fine, but no "login:" prompt: + + - Add getty entry to /etc/inittab for console tty. Look for + the "Adding console on ttyS<n>" message that tells you which + device is the console. + + "login:" prompt, but can't login as root: + + - Add entry to /etc/securetty for console tty. + + No ACPI serial devices found in 2.6.17 or later: + + - Turn on CONFIG_PNP and CONFIG_PNPACPI. Prior to 2.6.17, ACPI + serial devices were discovered by 8250_acpi. In 2.6.17, + 8250_acpi was replaced by the combination of 8250_pnp and + CONFIG_PNPACPI. + + + +[1] + http://www.dig64.org/specifications/agreement + The table was originally defined as the "HCDP" for "Headless + Console/Debug Port." The current version is the "PCDP" for + "Primary Console and Debug Port Devices." + +[2] + The HP MP (management processor) is a PCI device that provides + several UARTs. One of the UARTs is often used as a console; the + EFI Boot Manager identifies it as "Acpi(HWP0002,700)/Pci(...)/Uart". + The external connection is usually a 25-pin connector, and a + special dongle converts that to three 9-pin connectors, one of + which is labelled "Console." + +[3] + EFI console devices are configured using the EFI Boot Manager + "Boot option maintenance" menu. You may have to interrupt the + boot sequence to use this menu, and you will have to reset the + box after changing console configuration. |